The Minnesota Supreme Court recently held that it is reversible error to exclude an expert's opinion in its entirety, where only one of the three methodologies upon which that opinion is based is flawed. Kedrowski v. Lycoming Engines, No. A17- 0538, Minn. (Sept. 11, 2019). We previously reported on the intermediate appellate court's decision to affirm the wholesale exclusion of Don Sommer's opinion in the Summer 2018 edition of Aviation Happenings. The Minnesota Supreme Court now has reversed that decision.

This case arises out of the September 3, 2010 crash of a Glasair RG Super IIS. The NTSB determined that the accident was caused by the pilot's failure to maintain control of the aircraft in gusty wind. Plaintiff maintained, however, that he crashed because the engine lost power. Plaintiff retained Don Sommer as his accident reconstruction and aircraft design expert. Although Mr. Sommer had not previously overhauled or tested an engine-driven diaphragm-style fuel pump, he concluded that it failed to deliver adequate fuel to the engine because of design and manufacturing defects. His conclusions were based principally upon his own flow bench testing of the pump.

Mr. Sommer conceded that the pump was not defective if it met design specifications, which included production of certain fuel quantities at specified pressures and revolutions per minute (RPMs). However, he never tested the pump at those specified parameters. Mr. Sommer also conceded that the engine would receive adequate fuel if the pump was capable of producing outlet pressures between 10 and 22 psi, yet never tested it within those parameters.

Lycoming sought in advance of the trial to preclude Sommer's opinions, but the trial court deferred its ruling, allowing him to testify about his opinions and the bases therefor. The jury returned a verdict for plaintiff in the amount of $27.7 million. The trial court set that verdict aside, however, because it determined Mr. Sommer's testimony should have been excluded in its entirety due to the anomalies with his flow bench testing. The intermediate appellate court agreed and affirmed the entry of judgment for Lycoming as a matter of law.

On further review, the Supreme Court agreed that Sommer's flow bench test results properly were excluded. However, his ultimate conclusions that the fuel pump was defective and caused the accident also were based upon his "differential diagnosis." That is, he disassembled the engine and found nothing wrong with it. Having eliminated the engine as a potential cause of the alleged loss of power, the remaining explanation (to him) was a malfunctioning fuel pump. Additionally, Mr. Sommer's conclusions were based upon the pilot's testimony about the operating history of the aircraft, specifically, that on several occasions the engine would not operate on the engine-driven fuel pump alone, but needed assistance from the electrical boost pump.

The Supreme Court explained, "[W]e cannot see how the deficiencies in Sommer's flow-bench testing tainted Sommer's investigation as a whole. Sommer's differential analysis and interpretation of Kedrowski's boost-pump experience independently support his opinion that the defective Lycoming pump caused Kedrowski's power loss and crash." Because the trial court's improper admission of Sommer's flow bench testing results "might reasonably have influenced the jury and changed the results of the trial," the Supreme Court ordered a new trial on liability.

The Kedrowski decision is problematic for several reasons. First, it gives unwarranted weight and credence to Sommer's differential diagnosis methodology. That methodology is flawed in an aviation context because it assumes the existence of the very condition that is in question. In other words, Sommer began with the premise that the engine lost power, then assigned the most probable cause among the two or three potential causes that he considered.

Furthermore, there is no indication in the opinion that Sommer considered (and eliminated) other causes for the accident, including pilot error, air in the fuel lines, and improper fuel-air mixture. While it generally is true that a plaintiff is not required to disprove alternate causation theories, that should not be the standard where the expert's methodology itself requires differentiation among all possible causes.

Moreover, expert testimony generally is admitted where it adds something to the factual record and assists the factfinder in understanding scientific or technical concepts. Mr. Kedrowski himself was capable of testifying that the engine sometimes would not operate on the engine-driven fuel pump alone, and the jury was equally capable of inferring from that testimony that there could have been a malfunction with that component. Sommer's "testimony" and reliance upon that evidence hardly qualifies as scientific method and did not aid the jury in understanding something that otherwise was beyond their abilities.

Given the pronouncements of Kedrowski, it is difficult to imagine a scenario where an expert's testimony might be excluded in its entirety. As long as the expert's opinions are based upon several methodologies, and at least one of those methods has even a modicum of scientific or technical merit, the opinions will be admissible. Take heed.

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